1)
In 1974, a scientific report described a previously unreported nervous disease of goats which was believed to be caused by a virus. This was followed by a report of an arthritic disease in goats presumably caused by the same agent. Shortly afterward the viral cause of these conditions was confirmed and the virus characterized. The development of a diagnostic serologic test was soon reported along with the observation that a high percentage of goats in the United States appeared to have experienced the virus. Investigation into the transmission of the disease suggested that virus was spread through colostrum and milk of infected dams and that virus free herds might be maintained by raising kids in isolation.

2) Nomenclature
The nervous disease first reported in 1974, was named Viral Leukoencephalomyelitis of Goats (VLG). When it became apparent that arthritis could also result from the same virus infection, the name of the disease was changed to Caprine Arthritis Encephalitis Syndrome (CAE). It is now apparent that the virus also produces changes in the lung and udder. The name CAE however still remains in place.

3) The Causative Virus
Knowledge of how a disease is transmitted is often the key to developing a successful program for preventing the spread of infection. To date, all published reports suggest that goats become infected with CAE virus as newborn kids. Experimental evidence for this is persuasive. Kids delivered either naturally or taken by cesarean-section, but deprived of colostrum and fed cow milk remain free of the virus despite the fact that their dams are infected. If taken by cesarean-section or delivered naturally, but allowed to nurse colostrum or milk from an infected doe, kids will show evidence of virus infection. These findings indicate that kids are not infected in utero or during passage through the birth canal; but do pick up infection when nursing colostrum or milk from infected dams. This suggests that control of the spread of new infections might be achieved by separation and artificial rearing of kids at birth.

4) Transmission of CAE Virus
Knowledge of how a disease is transmitted is often the key to developing a successful program for preventing the spread of infection. To date, all published reports suggest that goats become infected with CAE virus as newborn kids. Experimental evidence for this is persuasive. Kids delivered either naturally or taken by cesarean-section, but deprived of colostrum and fed cow milk remain free of the virus despite the fact that their dams are infected. If taken by cesarean-section or delivered naturally, but allowed to nurse colostrum or milk from an infected doe, kids will show evidence of virus infection. These findings indicate that kids are not infected in utero or during passage through the birth canal; but do pick up infection when nursing colostrum or milk from infected dams. This suggests that control of the spread of new infections might be achieved by separation and artificial rearing of kids at birth.

5) Prevalence of CAE
One aspect of the CAE syndrome which has proven most troubling to
the US goat industry was a published report that a high percentage of
goats tested from all over the United States showed serological
evidence of infection with CAE virus. Of 1160 goats tested from 24
states, 81 showed antibody to CAE virus using the agar gel
immunodiffusion (AGID) test. It can be assumed that animals with
antibody to CAE virus have been exposed to and infected by the virus.
The only exception to this could be young kids with detectable antibody
picked up from the dam's co lostrum. Unlike most bacterial diseases,
where a strong antibody response means that the animal has cleared
itself of the invading organism, infections with CAE and other
retroviruses are likely to persist in the animal despite a high
antibody titer. Therefore, it is probably true that a large percentage
of antibody positive goats carry persistent infections. However, it does
not necessarily follow that the majority of these goats are likely to
show clinical signs of the CAE syndrome. The factors which contribute
to the onset of clinical signs in animals infected with the virus are
unknown.

6)
The major problem associated with this high prevalence of infected
US goats is not the actual incidence of clinical disease so much as the
negative perception of prospective goat buyers and regulatory
officials confronted with a positive AGID test. Already some countries
importing US goats, like Kenya, have refused or destroyed shipments of
goats which turned out to be antibody positive. Economic restraints such
as this increase pressure on the goat industry to aggressively tackle
the CAE problem.

7) The Clinical Signs of CAE
Two separate distinct syndromes are caused by the CAE virus, a
neurological disease in the spinal cord and brain of young kids and a
joint infection of older goats resulting in arthritis. How individual
animals infected with CAE virus escaped one or the other or both
syndromes remains a mystery. The clinical signs of the two syndromes
are as follows.

8) The Nervous Form of CAE
The nervous form of CAE was the first to
be described. All breeds of goats can be affected as can both sexes,
and most individuals first show signs between one and four months of
age. The problem is one of progressive weakness (paresis) of the hind
limbs leading to eventual paralysis. The early paresis may be
perceived as lameness, incoordination or weakness in one or both rear
legs. Knuckling over of the feet and difficulty in rising may follow
until such time that the animal is unable to rise at all. The course
of the disease is from several days to several weeks. Despite the
progressive paralysis, the kid will usually remain bright and alert and
continue to eat and drink. Mild pneumonia may be present. If the
correct diagnosis is made, the animal is often euthanized since there
is no known treatment for the condition.

9)
The development of these signs results from inflammation in the
spinal cord induced by the virus. Nerves which control motor function
of the hind limbs are progressively destroyed. In spite of the ongoing
inflammation, there is little or no change observed in the
cerebrospinal fluid on CSF tap nor in the complete blood count (CBC).
Diagnosis is based on recognition of the clinical signs and
confirmation depends on observation of the characteristic changes seen
microscopically in the spinal cord at the time of postmortem
examination.

10)
In older goats, a clinical variation of the nervous form of CAE has
been observed which is clinically indistinguishable from Listeriosis.
Signs include circling, head tilt and facial nerve paralysis. On
postmortem examination, the characteristic lesions of CAE virus are
found in the brain stem rather than the cervical spinal cord.

11) The Arthritic Form of CAE
The joint form of CAE most often
appears clinically between one and two years of age. There can be great
variability in the progression and severity of signs. Some goats can
be severely crippled within a few months while others may show only
intermittent lameness or stiffness for years without ever becoming
completely debilitated. A ''typical'' case would fall somewhere in
between. The disease is usually first recognized as a gradually
developing lameness accompanied or followed by swelling of the joints.
Swelling is most often noted in the front knees (carpi) and can also be
seen in the hock and stifle joints. As the condition progresses, joint
pain and stiffness become more apparent. The animal may spend a good
deal of time lying down, will begin to lose weight and develop a rough
hair coat. In severely affected joints, the range of motion may become
limited and goats are forced to walk around on their carpi. No specific
cure is known for CAE arthritis. The well-being of affected goats may
be improved by proper foot trimming, extra bedding and administration
of anti-inflammatory drugs such as aspirin.

12)
As in the nervous form, the complete blood count in goats with CAE
arthritis will most likely be normal. Fluid taken from affected joints,
however, may show changes suggestive of CAE. These include a reddish
brown discoloration, increased volume, low viscosity and an increase in
mononuclear cells. All joint fluid aspirates should be cultured for
bacteria, chlamydia and mycoplasma since these organisms can also cause
arthritis in goats. In addition to these infectious causes, traumatic
injury and poor conformation can also lead to joint problems. Keep in
mind, that not all swollen joints or stiff limbs are CAE arthritis.

13) Other Clinical Syndromes of CAE
Young kids with the nervous form
of CAE may show a concurrent pneumonia. On postmortem examination,
goats with either the nervous form or the arthritic form may show
characteristic changes in the lungs attributable to CAE virus
infection. These changes are described as interstitial infiltration of
mononuclear cells. Pneumonia due to CAE virus however is rarely seen as
the only clinical sign in infected goats.

14)
Another interesting microscopic finding from postmortem examination
is a similar mononuclear infiltration of the mammary gland of infected
does. There is some speculation, but no certain confirmation, that the
well known condition of hard udder seen in some does at freshening may
be due to CAE virus. This mysterious condition is often misdiagnosed
as udder edema or mycoplasma mastitis.

15)
In arthritis of goats due to CAEV, clinical signs are limited to
the joints and surrounding structures. Affected goats may initially show
soft fluid swellings over the joints, especially in the bursae of the
front knees. Over a period of weeks to months pronounced lamenss may
develop and progress to the point where animals are unable to extend the
limbs and may walk on their knees. Radiographs may reveal extensive
calcification of the soft tissues surrounding the joint. Joint fluid
will contain excessive numbers of mononuclear cells. Postmortem
examination will reveal extensive proliferation of the synovial
membrane. In other animals the advance arthritic signs may not be so
severe and these animals show only intermittent pain, reluctance to move
and progressive weight loss.

16)
A serum test can be run which demonstrates that the goat has been
exposed to the virus, but the test will not absolutely confirm that
arthritis is due to the virus infection. No treatment or vaccine is
available for arthritis due to CAEV. A separate chapter on CAE follows
because of its importance.

17) Prevention and Control
Suggestions for the control of CAE infection and plans for the
establishment of CAE free herds have been published. These plans are
based on current knowledge concerning the transmission of the virus
and controversy has arisen regarding the practicability and
effectiveness of these programs. Perceptions of how reasonable these
suggestions are, may depend largely on the interest to establish a CAE
virus free herd. A hobbyist with two grade does in the backyard for
home milk consumption may not be motivated sufficiently to change the
management in order to raise CAE free kids. On the other hand, an
internationally reputable breeder with sales of registered stock may in
fear of a positive AGID test want strongly to establish and maintain a
CAE free herd. A control plan would include the following:

1. A serologic survey of all animals presently in the herd.

2. Culling of all AGID positive animals if economically feasible.

3. Repeated AGID testing at 6 month intervals to insure that all
positive individuals were identified.

4. If some or all AGID positive animals are maintained for the time
being, the strategy then shifts to the creation of a new CAE free
herd founded with the next kid crop.

5. At the next kidding season all births are observed and the kids
are removed from their does immediately. These kids are either
deprived of colostrum, fed only frozen colostrum from does
previously identified as AGID negative, or fed pasteurized
colostrum. Only experienced herdsmen with a strong background in
kid rearing should attempt to raise colostrum deprived kids since
these animals are susceptible to a variety of dangerous infections
if not given protective immunoglobulin injections. Pasteurization
of colostrum is considered a poor alternative because heating to
161F causes the liquid colostrum to congeal. Slow pasteurization
at 131F for 1 hour may minimize this problem but this is time
consuming. Feeding colostrum from AGID test negative does may be
the best compromise although it must be pointed out that an
occasional seronegative doe may actually be shedding the virus
and a small number of new kids may be infected.

6. Kids should be raised in separate quarters from does and fed cow
milk or milk replacer until weaning.

7. All kids should be tested at 6 months of age and periodically
thereafter to insure their seronegative status. Seropositive
animals should be culled immediately.

8. As the new replacement herd matures, older previously
seropositive animals, still in the herd, should be systematically
culled. Any animal showing clinical signs of CAE should be culled
immediately.

9. In this manner the incidence of CAE in a herd can be dramatically
reduced in one generation and possibly eliminated in a few
generations. For this to occur, conscientious adherence to the
program is necessary.

18)
Hopefully research into the workings of CAE virus will continue at
the same dynamic pace observed over the last eight years. Clarification
of the mechanisms of transmission and the animal's responses to infection
could lead to better recommendations for control of the disease and

About the author: Extension Goat Handbook - This material was contributed from collections at the National Agricultural
Library. However, users should direct all inquires about the contents to
authors or originating agencies. D. M. Sherman; U. of Minnesota, St. Paul., S. B. Guss; Pennsylvania State U., Unversity Park.